1. Field of the Invention
This invention relates generally to the field of disinfectants, and relates more specifically to using hypochlorous acid solutions as pathogen management systems in, for example, a poultry processing system to limit poultry contamination.
2. Background of the Invention
Chlorination is known method for killing undesirable microorganisms. Chlorine may be provided in multiple forms including chlorine gas (Cl2), sodium hypochlorite liquid, calcium hypochlorite powder or granules, or isocyurantes. Chlorine gas (Cl2) is a relatively cheap and highly effective antimicrobial agent; however, it is also a highly toxic and corrosive gas. Hypochlorites such as NaOCl or Ca(OCl)2 are a much safer alternative, but are considerably more expensive that gaseous chlorine. Finally, hypochlorite solutions (i.e., bleach) may also be utilized, however these are rarely used in large scale Water treatment applications because they are bulky and expensive. Regardless of the chlorine source, hypochlorous acid (HOCl) and the hypochlorite ion (OClxe2x88x92) are the final desirable antimicrobial products.
One method of forming HOCl occurs when Cl2 is dissolved in water. The reaction proceeds according to the following equation:
Cl2+H2OHOCl+H++Clxe2x88x92xe2x80x83xe2x80x83(1) 
Another method for producing HOCl uses metal hypochlorites dissolved in water. The reaction proceeds according to the following equation:
NaOCl+H2ONaOH+HOClxe2x80x83xe2x80x83(2) 
This method is generally utilized by common household hypochlorites and generates HOCl on a relatively small scale.
HOCl is a weak acid and will dissociate. In aqueous solution, HOCl and OClxe2x88x92 are generally present in a pH dependent equilibrium:
HOClH++OClxe2x88x92pKa=7.53xe2x80x83xe2x80x83(3) 
At low pH, HOCl is the predominant form, while at high pH, OClxe2x88x92 predominates. The HOCl form is about 80 times more effective than OClxe2x88x92 for killing microorganisms because HOCl crosses cell membranes easier than the hypochlorite ion. Accordingly, it would be desirable to control the pH of the chlorinated solution to increase the antimicrobial effectiveness of the chlorination process.
One particular use of chlorination is to kill undesirable microorganisms in poultry processing systems. Since much of the poultry processing involves moving the bird on conveyers and human contact, provisions must be made to keep both the equipment and personnel sanitized.
For example, Salmonella is one of the most important causes of foodborne disease worldwide. In many industrialized countries the incidence of salmonellosis in humans and the prevalence of Salmonella in many food products have increased significantly over the last twenty years. Salmonella bacteria have a broad host-spectrum, and can be isolated from a wide range of animal species, including birds and reptiles. The animals usually are healthy carriers, and contaminated feed plays an important role in the epidemiology 5 of salmonellosis. Salmonella can survive for a long time in the environment. Humans are usually infected through consumption of contaminated foods of animal origin. However, other food such as fresh produce, seafood and chocolate have also been implicated in outbreaks because of cross-contamination, use of contaminated water, use of manure as a fertilizer, presence of animals or birds in the production area or other factors.
In a typical poultry processing operation, freshly laid fertile eggs are collected and incubated. After they hatch, chicks are delivered to farms, reared until ready for slaughter and then transported to a processing plant. At the plant, the process of slaughtering includes several phases from unloading and shackling the live birds to grading and packaging the carcasses. Then, carcasses are shipped and distributed chilled or frozen while some poultry carcasses are used for portioning and/or to produce a variety of raw or processed products. The microbiological condition of poultry carcasses is highly dependent on the manner in which animals are reared and slaughtered. The microbiological condition of live birds influences the microbiology of the products and the live animals are the principal source of microorganisms found on poultry carcasses. At the processing plant, the conditions of slaughtering will further influence the extent to which processed poultry will be contaminated.
There are many sources of contamination during poultry processing. Commercially grown poultry flocks are collected on the farm, placed into crates, transported to the processing plant and slaughtered on the same day. Contaminated crates can be a significant source of Salmonella and E. coli on processed carcasses. Contamination of feathers with microorganisms of fecal origin increases as birds are confined in crates for transport to the plant and microorganisms in feces and on feathers can be spread from bird to bird within the crates. Stress of transportation may amplify the pathogen levels. In one study, fecal droppings collected in broiler houses about one week prior to slaughter were contaminated at a rate of 5.2% while Salmonella was found in 33% of the samples collected from live-haul trucks at the processing plant.
During hanging, as feathers, feet and bodies are contaminated with a variety of bacteria, wing flapping creates aerosols and dust, contributing to contamination of the unloading zone and transmission of pathogens at this stage.
Stunning and killing have few microbiological implications, although electrical waterbath stunning may lead to inhalation of contaminated water by the birds and microbial contamination of carcass tissues.
During scalding, soil, dust and fecal matter from the feet, feathers, skin and intestinal tract are released into the scald water and thus provide a significant opportunity for cross contamination. A large variety of bacteria, e.g. Salmonella, Staphylococcus, Streptococcus, Clostridium spp. have been isolated from scald water or from carcasses or air sacs immediately after scalding.
Bacterial survival in the scald water is influenced by scald temperature and time. The lethal effect of water held at 60xc2x0 C. (hard scald) used for carcasses intended for water chilling is measurable and greater than the lethal effect of water held at lower temperatures, e.g. 50-52xc2x0 C. (soft scald) as used for carcasses that will be air chilled.
It has also been demonstrated that scalding results in modifications to the poultry skin: removal or damage of the epidermal layer, exposing a new surface for contamination which is smoother and less hydrophobic, exposure of microscopical channels and crevices. During and after scalding, the skin surface retains a film of scalding water which contains organic matter and large numbers of bacteria. Some of these bacteria may adhere more easily to the modified surface of the skin. Some may be retained in the channels or crevices on the skin surface as well as in the feather follicles. During the following stage of defeathering, there may be entrapment of bacteria in the channels, crevices and follicles. When entrapped, the bacteria may be difficult to remove by subsequent procedures, including mechanical and chemical decontamination treatments; they also display greater heat resistance.
Defeathering with automatic machinery may be expected to cause considerable scattering of microorganisms in particular via aerosols. Early findings, from work being carried out in the United Kingdom, indicate that these aerosols from defeathering can be reduced by altering the design of the equipment. Conditions inside the machines are favorable to the establishment of a biofilm and colonization by pathogens, in particular S. aureus which can survive, multiply and become indigenous to the equipment. Defeathering has been recognized as a major source of carcass contamination with S. aureus, Salmonella, Campylobacter spp and E. Coli. Several studies have established that the microbial populations on poultry carcasses reflect the microbiological condition of the carcasses immediately after defeathering.
Evisceration can give rise to fecal contamination with enteric pathogens such as Salmonella, Campylobacter and Cl. perfringens, especially when intestines are cut and/or when automatic machines are not set properly. In addition, microorganisms may be transferred from carcass to carcass by equipment, workers, and inspectors.
Spray washing of carcasses removes visible fecal contamination and some microorganisms such as Salmonella and E. Coli. However, it does not eliminate those bacteria that have become attached to the carcass surface or entrapped in the inaccessible sites of the skin surface. It has been demonstrated that continuous carcass washing or applying a series of sprays at the various stages of evisceration removes bacteria before they are retained, and this is much more effective than a single wash after evisceration. There is a danger that use of water sprays, in particular those used in carcass washing, may create aerosols that can spread microbiological contamination.
Three types of chilling processes may be used: air blast, water immersion and a combination of air and water chilling. All three methods may lead to some degree of cross contamination. With regard to the final microbiological load on the carcass, it has been demonstrated that properly controlled water immersion chilling can reduce overall levels of carcass contamination. However, high levels of contamination of carcasses before chilling and insufficient water used per carcass (amount of fresh water replacement; number of carcasses in relation to the volume of chilled water) may result in an increase in the level of microbial contamination on carcasses rather than a decrease.
There have been numerous studies to determine the relative effect of each processing step on carcass contamination. Generally, the results show that aerobic plate counts or count of Enterobacteriaceae decrease during processing.
The data on the prevalence of Salmonella contaminated carcasses are highly variable. The proportion of contaminated carcasses appears to be influenced mainly by the condition of incoming birds and also by processing. Although the prevalence of Salmonella contaminated carcasses can be high, the number of Salmonella per carcass is usually quite low. In comparison with Salmonella, campylobacters are generally carried in high numbers by poultry. Therefore carcasses are more readily contaminated during processing and the numbers present are correspondingly higher.
Antimicrobial compounds have been used for disinfecting products and equipment surfaces for many years. Some of the antimicrobial compounds that have been approved for use are: hot water, steam, lactic acid spray, acetic acid spray, citric acid spray, trisodium phosphate, chlorine dioxide, acidulated sodium chlorite, and sodium hypochlorite (bleach). Hot water is generally not used with poultry products because hot water can scorch surfaces, resulting in a xe2x80x9ccookedxe2x80x9d appearance. This is especially crucial if the end product is to be deboned unfrozen or fresh breast fillets. Steam pasteurization procedures have recently been developed and have been shown to be very effective against bacteria; however, applying steam to individual carcasses moving down a processing line at 70 to 140 carcasses per minute is challenging. Thus, the industry has been slow to incorporate this type of treatment.
Organic acids are excellent for killing bacteria because they penetrate and disrupt the cell membrane and dissociate the acid molecule, thereby acidifying the cell contents. They are stable in the presence of organic material, such as blood or feces and they are fairly inexpensive to use. Acids are susceptible to water pH problems (such as high incoming water pH), they may cause product defects, such as off flavors, odors, and colors, even when used at low levels. Additionally, organic acids may corrode equipment.
Trisodium phosphate (TSP) is becoming more widely accepted and used, because the USDA is encouraging its use within the industry. TSP is costly to use because of the quantity needed to disinfect carcasses. There are negative aspects to using TSP in poultry processing plants that should be considered. Residual TSP on carcasses causes the chiller water pH to increase dramatically. In plants where TSP is used, the chiller water will generally be in the pH range of 9.7 to 10.5. This is extremely high and completely eliminates the ability of chlorine to become its effective form, hypochlorous acid. Hypochlorous acid forms most effectively when water is in the pH range of 5.5 to 7.0. Thus, plants using TSP may as well be dumping their bleach down the drain. This is not a desired situation because chlorine is very effective against Salmonella. In fact, plants in the Southeastern U.S. that have installed a TSP system have often seen their Salmonella and E. Coli prevalence increase when compared to levels prior to using the TSP. This is most likely due to the TSP washing Salmonella off of one carcass and it is then able to spread to other carcasses. Scientists have reported that Listeria monocytogenes is resistant to the effects of trisodium phosphate (TSP), and exposure to a high (8%) level of TSP for 10 minutes at room temperature is required to reduce bacterial numbers by 1 log10 after a colony has grown on a surface and a protective layer (biofilm) has been formed.
Chlorine dioxide has been evaluated in processing plants and seems to be effective for killing bacteria at very low concentrations; however, it is expensive to generate and very difficult to maintain at a particular concentration in chiller water. Some USDA inspection personnel have been reticent to allow its use in plants.
Sodium hypochlorite (bleach) is by far the most widely used chemical sanitizer in the poultry industry. It is excellent for killing bacteria and is inexpensive; however, as mentioned previously, it forms its most effective bacteriocidal agent, hypochlorous acid, in the pH range of 5.5 to 7.0. Thus, when used in combination with a TSP system, bleach is generally ineffective. Chlorine is inactivated in the presence of organic material. Residual blood and feces in the chiller can greatly affect how well chlorine is able to kill bacteria on carcass surfaces. It is essential to maintain proper flow rate in the chiller to reduce organic material sufficiently to allow the chlorine to be effective.
As discussed, chlorine is available in several forms: gas, liquid, and powder. The choice is usually dependent upon the volume of water to be treated, the amount of disinfection required, and the area in which the chlorine will be used.
Chlorine gas is considered the best choice where large volumes of water are to be chlorinated at high levels (4-5 ppm). Chlorine gas is pure 100% available chlorine, it lowers the pH slightly, and is easy to control and apply. Economically, it is the least expensive source on the basis of available chlorine.
Conventionally, hypochlorites (calcium and sodium) are second in choice because chemical dosage is difficult to control. Hypochlorites raise the pH of the water, which in hard water, may cause deposits on equipment. Hypochlorites are more sensitive to organic matter in water resulting in a faster loss of germicidal power. Being unstable, hypochlorites are difficult to store and deterioration results during storage. Hypochlorites are a good choice, however, when only small amounts are needed, such as localized germicidal application for clean-up and preventing slime formation on belts and other equipment.
Despite the several known processes for producing hypochlorous acid and pathogen management, there remains a need for a quick, safe, and efficient process for producing hypochlorous acid solutions suitable for use as a disinfectant in poultry processing.
The present pathogen management system improves the conventional art of controlling pathogens on a target element (for example, a poultry product in a poultry processing line) by subjecting the bird to a disinfectant, the improvement comprising subjecting the target element to hypochlorous acid. Preferably, the present invention comprises utilizing a hypochlorous acid stream of between about 4.3 and 7.0 pH as a pathogen reduction agent. For example, the present system preferably can provide a poultry carcass exiting a post chiller of a poultry processing system as clean, or cleaner, both organically and microbially, than the carcass being off line processed using standard FSIS techniques.
As a pathogen management system used with poultry processing, preferably the present invention comprises a three control point approach to pathogen reduction. When a carcass is received into the pick/kill area, many pathogens are present on this carcass. Pathogen control begins in this area by the application of hypochlorous acid. At other locations of the poultry processing, a similar use of hypochlorous acid is applied so the plant can control the pathogen throughout.
The first critical control point is located in the pick/kill room. A first washing system is placed post picking. The first washing system washes the carcasses completely (feet to head) using mechanical brushes and strategically positioned sprays with hypochlorous acid before the carcass enters the processing area. The purpose of this point controls Salmonella, Escherichia coli and organics on the exterior of the carcass. This control point helps control the pathogens and organics entering the processing area that are coming from grow-out or farms.
The second critical control point is located after the carcasses have been processed through evisceration. After the final wash system (IOBW), a second washing system is added. The second washing system washes the carcasses completely (hocks to tips of wings) both mechanically and by sprays with hypochlorous acid before the carcass enters the chilling area. The purpose of this point controls Salmonella, E-Coli and organics on the interior and exterior of the carcass. This control point also helps control the pathogens and organics entering the chiller area that are coming from evisceration.
A third critical control point is located in the chilling system. This control point is set up to reduce the existing pathogens on and inside the carcass and prevent cross contamination of the carcass in the chiller water. By adding hypochlorous acid to the chillers and maintaining available free chlorine in the chiller water, pathogen control is completed.
Preferably, the hypochlorous acid is generated by a pressurized solution system that produces a carbonic acid solution, using carbon dioxide gas and a make-up water source, prior to injecting into the chillers or washing systems. The carbonic acid is mixed with a chlorinated solution to form hypochlorous acid. The combination of the carbonic acid solution and the chlorinated solution can form up to a 98% hypochlorous acid solution that is injected into the chillers or washing system that will enhance the kill of foodborne pathogens.
Accordingly, it is an object of the present invention to provide a pathogen management system utilizing hypochlorous acid.
It is yet a further object of the present invention to provide a pathogen management system utilizing hypochlorous acid stream at a pH of between about 4.3 and 7.
These and other objects, features and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawing figures.